I'm mid-plat and just recently climbed out of gold soloq, and I dipped into silver at the start of the season too. I honestly can say you don't need to coordinate anything.

Give a general direction for team to go in, so left or right. After that, everyone's going to go do whatever they want to do and there's not much you can control from there.

Just do hero callouts for the shit that needs to be taken care of.

Getting fucked by pharah? Say phara + her location. Location is important.

Saying "kill phara pls" or along the lines doesn't help. We all know she needs to die. It's such a common occurrence and why Pharah is such a rampant pub stomper in gold/plat. Just people unaware of how to phrase information in a useful way.

Anti-heal on their tanks? Call it out.

Healers dead? Call it out.

People usually respond well to that sort of stuff. Some people don't even pay attention to kill feeds or don't even have it enabled, so pointing that out helps indicate when your team should take initiative and actually do things.

Also playing Zen is really nice for directing your team, if you really need to, because people generally focus fire on your discord callouts.